Ultra Q (1966)

Ultra Q can be described as a half-hour Toho kaiju film. Although series creator Eiji Tsuburaya intended this series to be more like The Twilight Zone and focus less on the monsters, TBS convinced Eiji to add more monsters onto the show, as Godzilla (Gojira) and Gamera were very popular at the time (the first "Kaiju Boom" was already born). This series predates The X-Files, with continuing characters who investigate strange supernatural phenomena, be they giant monsters, aliens, ghosts, and other assorted calamities. The single best comparison to any American TV show is to The Outer Limits, which in its original form generally featured a monster-of-the-week story.